This invention relates in general to concrete work and more particularly to an improved concrete slab construction and a method of constructing a slab in a building having an upright column standing on a pier footing.
In many types of construction, building posts or columns serve a significant load bearing function. For example, posts are often installed in basements and other areas to support beams which in turn provide support for overlying parts of a building. In order to provide a stable footing for such posts and to prevent moisture, frost heave and other forces from displacing them, the posts are typically installed on concrete pads or piers which are set into the ground, often to a considerable depth in order to bear the load and resist frost heave.
When a basement floor or other concrete slab is poured, it is necessary to isolate the post from the slab. Otherwise, if the slab is pushed upwardly by moisture induced expansion of the soil or is otherwise displaced, the post can be displaced with it and lead to major structural problems in the building. To avoid this, isolation of the post is required so that the slab can move independently of the post and the pier which underlies it.
It is common practice for workers to place a tube or a bucket on the pier so that when the slab is poured, the bucket or tube creates a round cavity in which the base of the post can be placed when the post is installed. A disadvantage to this practice is that it involves several steps, including placement of the bucket, removal of the bucket after the slab has been poured, and subsequent filling of the hole around the post with additional concrete. When pouring the additional concrete, it is difficult to match the finish of the floor and maintain a flat grade. The need for so any different steps in the building procedure, all at different times, also delays the process and adds to its cost. Even then, there is often incomplete isolation of the post and pier from the slab. A bucket or tube also has the disadvantage that it cannot be placed around a post that is already in place.
Another practice that has been used involves constructing a wooden box around the post and using the box as a form to separate the slab from the column and pier. The advantage of such a box is that it can be built around a post that is already in place. The disadvantages include the considerable time that is required to construct the box and a tendency for the concrete to crack in the corner areas of the box. The problems encountered in using an isolation box type form are similar to those encountered when using a bucket.
The present invention is directed to an improved concrete slab which makes use of a unique ring structure to isolate a building post from the slab. The invention is also directed to a method of using the ring for efficient and effective construction of the slab.
In accordance with the invention, a specially constructed ring can be placed on a concrete pier to extend around the location of a post or column which is to be supported on the pier. Concrete is poured outside of the ring to form a basement floor or other slab, and also inside of the ring, either around a column that is set directly on top of the pier or in a manner to completely fill the ring so that a column can subsequently be set on the concrete which fills the ring. The result of this construction technique is that the ring is embedded in the concrete slab and provides effective isolation of the column from the part of the slab located outside of the ring. Consequently, displacement of the slab does not displace the column to possibly create structural problems in the upper part of the building. Instead, the concrete located inside of the ring remains in place even if the slab shifts elsewhere. At the same time, all of the concrete can be poured at a single time in a single step to expedite the construction process and make it more efficient than in a case where multiple steps are required.
The construction ring preferably exhibits various features which enhance its utility and versatility. It may be tapered from bottom to top to prevent upward displacement of the slab outside of the ring from creating displacement of the concrete inside of the ring. This assures effective isolation of the column from the slab and reduces shear forces.
Another feature of the ring is that it may have overlapping ends which are detachably connected so that the diameter of the ring can be adjusted in accordance with the size of the column and other particularities that may be involved. This feature accommodates columns of different diameters and also allows the same ring to be used in a variety of different applications and with a variety of different types and sizes of columns.
The height or depth of the ring may be made adjustable. The ring can have detachable tear strips that allow its height to be reduced when the tear strips are removed. For example, a ring may be used for a 4xc2xdxe2x80x3 slab, and a ring having the same construction can also be used for a 3xc2xdxe2x80x3 slab simply by removing one or more of the tear strips.
A fastening foot may be provided on the ring to allow it to be readily fastened to the underlying pier. The foot may take the form of a tab which can be folded from the lower edge of the ring so that it lies flatly on top of the pier. A concrete nail or other fastener can then be applied to secure the ring in the desired position on the pier. The ring can be accurately held in a concentric relationship to the post while the concrete is being poured and is not susceptible to being dislodged by the force of the concrete or other forces. Consequently, the post can be accurately centered in the ring in the final slab structure, and this results in a sound overall construction.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.